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Tribochemical Mechanism of Borate of Triethanolamine in Water Solution by XPS
Du, Da-Chang,Kim, Seock-Sam,Suh, Chang-Min Korean Tribology Society 2001 KSTLE International Journal Vol.2 No.2
Tribological behaviors of a borate of triethanolamine in water solution were evaluated using a four-ball wear tester. X-ray photoelectron spectroscopy (XPS) was employed to study tribochemical species on worn scars of steel balls. Results show that a thick deposit layer was produced on the worn scars, which came from the decomposition of the borate. The surface film on the worn scars was mostly consisted with H$_3$BO$_3$, B$_2$O$_3$and large amounts of ferricyanides.
Antioxidation action of ZnDDP blended with MoDDP in mineral oil
Da-Chang Du,Kim, Seock-Sam,Chun, Jung-Sik,Suh, Chang-Min,Kwon, Wan-Seop 경북대학교 트라이볼로지연구소 2001 INTERNATIONAL SYMPOSIUM ON HIGH PERFORMANCE OF TRI Vol.2001 No.-
The flow analyzed is that of viscous gas within a clearance of binary thrust bearing with spiral grooves having identical geometry at both working surfaces. The boundary conditions for velocity take into account the slip effects of the first and second orders according to Cercignani-Sliozkin method. The essentially nonlinear equation is obtained for determination of dominating pressure in active zone of binary models; the equation is fit for a wide range of Knudsen numbers. The algorithms are developed for calculation of the integral characteristics of binary thrust bearing. The refined data are presented concerning the optimal parameters and advantages of binary bearings. According to the optimization data the computational tables are constructed which permit to realize the design of the experimental models of binary thrust bearing without additional calculations.
Oxidation behavior of YAG-ZrB2 ceramics prepared by spark plasma sintering
Jie-Guang Song,Da-Ming Du,Yin-Yan Ju,Yang-Liang Li,Shi-Bin Li,Gang-Chang Ji 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4
ZrB2 and YAG are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To make ZrB2 ceramics have better oxidation resistance, high-density YAG-ZrB2 ceramics were prepared. The oxidation behavior of YAG-ZrB2 ceramics is investigated at different temperatures. The results indicate that the enhanced weight change differs according to the temperature range, slightly in the temperature 900-1000oC, sharply from 1100-1300 and smoothly above 1300oC. The weight change rate of YAG-ZrB2 ceramics is increased by prolonging the oxidation time, but the weight change rate of YAG-ZrB2 ceramics is gradually reduced. The oxidation layer is porous as compared to the YAG-ZrB2 ceramics layer.
이다애(Da-Ea Lee),유경두(Gyeong-Du Yu),정창호(Chang-Ho Jung),강성웅(Seong-Woong Kang),주현찬(Hyeon-Chan Joo),조종두(Chongdu Cho) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The disk brake system of a vehicle dissipates its kinetic energy as heat. This energy conversion is notoriously well known as one of most difficult phenomena to analyze. And the contact performance is an important issue especially to the brake system of high-speed railway trains mainly due to the unstable contact between brake disks and brake pads at high speed that causes severe frictional heat concentrated at a point and may develop hot spots on the disk surface. These hot spots are followed by thermal cracking and uneven wear of brake disks and brake pads and shortening their service life. In this study, thermo-mechanical analysis is conducted on different railway brake pad models using Abaqus FEA software to compare thermo-mechanical behavior according to the shape of the brake pads. In the analysis, the contact performance is compared by analyzing the contact pressure distribution of friction material surfaces of each model.
Preparation and properties of ZrB2-YAG-Al2O3 ceramics
Jie-Guang Song,Gang-Chang Ji,Shi-Bin Li,Yang-Liang Li,Da-Ming Du,Lian-Meng Zhang,Yin-Yan Ju 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4
ZrB2, YAG and Al2O3 are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To achieve better properties in ZrB2 ceramics, high-density ZrB2-YAG-Al2O3 ceramics were prepared. Below 1000℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is less than that of ZrB2-YAG ceramics. From 1000℃ to 1600℃, the second largest shrinkage occurs. Above 1600℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is more than that of ZrB2-YAG ceramics. The fracture toughness of sintered ceramics from coated raw materials is higher than that of sintered ceramics with mixed raw materials with the same phases and phase content, the fracture toughness of ZrB2-YAG-Al2O3 ceramics is higher than that of ZrB2-YAG ceramics with the same raw materials. The weight gain of all types of ceramics is increased with all increase in the oxidation temperature, the weight gain of ceramics is reduced with all increase in the YAG-Al2O3 content and Al2O3 proportion, especially above 1500℃. ZrB2, YAG and Al2O3 are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To achieve better properties in ZrB2 ceramics, high-density ZrB2-YAG-Al2O3 ceramics were prepared. Below 1000℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is less than that of ZrB2-YAG ceramics. From 1000℃ to 1600℃, the second largest shrinkage occurs. Above 1600℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is more than that of ZrB2-YAG ceramics. The fracture toughness of sintered ceramics from coated raw materials is higher than that of sintered ceramics with mixed raw materials with the same phases and phase content, the fracture toughness of ZrB2-YAG-Al2O3 ceramics is higher than that of ZrB2-YAG ceramics with the same raw materials. The weight gain of all types of ceramics is increased with all increase in the oxidation temperature, the weight gain of ceramics is reduced with all increase in the YAG-Al2O3 content and Al2O3 proportion, especially above 1500℃.
Effect of raw materials on the properties of ZrB2-YAG-Al2O3 multi-phase ceramics
Jie-Guang Song,Fang Wang,Da-Ming Du,Yin-Yan Ju,Shi-Bin Li,Gang-Chang Ji,Lian-Meng Zhang 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.2
ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures, but ZrB2 ceramics is difficultly sintered and easily oxidized. To make ZrB2 ceramics possess the high relative density and the better oxidation resistance. The effects of raw materials on the properties of ZrB2 composite were investigated. YAG and Al2O3 help for the densification of ZrB2 ceramics. Fracture toughness of sintered ceramics with coated powder is higher than that of sintered ceramics with mixed powder. The mechanical property of ZrB2-YAG-Al2O3 materials is higher than that of ZrB2-YAG materials. Oxidation layer thickness of sintered ceramics with coated powder is thinner than that of sintered ceramics with mixed powder. These results show the sintered ZrB2 based multi-phase ceramics with coated microstructure help to increase the mechanical properties and oxidation resistance. The oxidation resistance of ZrB2-YAG-Al2O3 ceramics is better than that of ZrB2-YAG materials.